Iam trying to implement ternary tree in java but i have got exception in printnode method..i couldnot figure out the exception it will be great help if any one help me to figure out this Thanks in advance here is the the code
exception
Exception in thread "main" java.lang.NullPointerException
at TreeStructure.printNode(TreeStructure.java:67)
at TreeStructure.printNode(TreeStructure.java:64)
at TreeStructure.runTree(TreeStructure.java:95)
at TreeStructure.main(TreeStructure.java:109)
public class TreeStructure
{
public Node root;
/**
* @param args
*/
public void insert(Node node, String value)
{
if(value.compareTo(node.value)<0)
{
if (node.left!=null)
{
insert(node.left,value);
}
else
{
System.out.println("Inserted"+value+"to left of"+ node.value);
node.left=new Node(value);
node.left.parent=node;
}
}
else if(value.compareTo(node.value)>0)
{
if(node.right!=null)
{
insert(node.left,value);
}
else
{
System.out.println("Inserted"+value+"to right of "+node.value);
node.right=new Node(value);
node.right.parent=node;
}
}
else if(value==node.value)
{
if(node.middle==null)
{
insert(node.middle,value);
}
else
{
System.out.println("Inserted"+value+"to middle of"+node.value);
node.middle=new Node(value);
node.middle.parent=node;
}
}
}
public void printNode(Node node)
{
if(node!=null)
{
printNode(node.left);
System.out.println("Tree traversal"+node.value);
}
if(node.parent!=null)
{
System.out.println("parent is"+node.parent.value);
}
else
{
System.out.println("");
printNode(node.middle);
printNode(node.right);
}
///need to add some code here
}
public void TestInsert(Node start)
{
System.out.println("Testcase Insert");
insert (root,"Astana");
insert(root,"Asgrad");
insert(root,"Lychs");
insert (root,"Brac");
insert(root,"London");
insert(root,"Arad");
insert(root,"Kathmundu");
printNode(start);
}
public void runTree()
{
root=new Node("Asgrad");
System.out.println("Tree build with"+ root.value);
printNode(root);
TestInsert(root);
}
public static void main(String[] args)
{
// TODO Auto-generated method stub
TreeStructure tree=new TreeStructure();
tree.runTree();
}
}
// here is node class
public class Node
{
Node parent;
Node left;
Node right;
Node middle;
String value;
public Node(String value)
{
this.parent=null;
this.left=null;
this.right=null;
this.middle=null;
this.value=value;
}
}
